The liquefaction of solid carbonaceous material, such as coal, in the presence of a solvent has been practiced since the early years of the twentieth century. Such liquefaction or solvent refining process has been performed predominently on a non-commercial basis due to the expense of performing the process to derive utilizable liquid and solid fuels and because of the relatively less expensive availability of liquid fuels from petroleum. Large scale production of liquefied fuels from coal was performed in Germany when petroleum was unavailable to that country during the war years.
With the increasing expense and scarcity of petroleum and the liquid fuels derived therefrom, increased interest in the liquefaction or solvent refining of solid carbonaceous materials, such as coal, to liquid and solid refined products has occurred. However, the technical difficulties in achieving high yields of liquid products from coal at relatively economical rates has still presented a problem for those in the art. The most popular solution to the production of high yields of the desired liquid products from solid carbonaceous material, such as coal, has been the use of metal catalysts such as molybdenum, cobalt, nickel, tungstun oxides and sulfides. Such catalysts improve the proportion of liquid product as well as the overall conversion of coal to solid refined products, known as solvent refined coal (SRC) and oils. However, these metal catalysts are expensive and constitute an undesirable increase in the cost of liquid fuel production from solid carbonaceous material or coal. This is particularly true of coal conversion reactions wherein increased carbon fouling and metal and sulfide contamination of catalysts over that expected in petroleum refining occurs, with the resulting effect of diminishing the effective life of the catalyst in the reaction zone. This requires either the regeneration of the fouled metal catalysts or the disposal of the catalyst and the replacement of the same with additional fresh catalyst. When such expensive metal catalysts are utilized, both of these modes of operating the catalyzed reaction of coal are deemed to be undesirable from an economic point of view when operating the coal liquefaction process in a commercial manner wherein the resulting liquid product must be competitive with the remaining petroleum products still presently available. One alternate solution to this problem has been to utilize inexpensive coal liquefaction catalysts which can be thrown away after their effective catalytic life has expired without adversely affecting the economic operation of a commercially run coal liquefaction process. The difficulty in this solution is that many relatively inexpensive catalysts do no have significant or desirable levels of catalytic activity for the liquefaction of coal or other solid carbonaceous material. Because of this drawback, yet another attempt at a solution to the creation of an economic and efficient liquefaction process has been the combination of relatively inexpensive catalysts with small amounts of expensive catalysts.
For example, in U.S. Pat. No. 1,946,341, the hydrogenation of petroleum and coal tars in the presence of hydrogen sulfide and a metal sulfide catalyst, such as iron, cobalt or nickel sulfide is set forth.
Alternately, in U.S. Pat. No. 2,227,672, a process for the thermal treatment of carbonaceous materials, such as oil or coal is set forth wherein a co-catalyst system is utilized. Preferably, a large proportion of inexpensive catalyst of low activity is combined with a small proportion of a relatively expensive catalyst of high activity. The inexpensive catalysts include various metal sulfides such as ferrous, manganous and zinc sulfides. The expensive catalyst are generally chosen from the disulfides of tungsten, molybdenum, cobalt and nickel. Such catalysts can be supported on a carrier and activated by various acid treatments or gas treatments such as hydrogen contact. Such catalysts can be utilized for the destructive hydrogenation of coal as recited in the text of the patent.
In U.S. Pat. No. 2,402,694, the use of iron sulfide catalysts is recited for the production of thiols, wherein the iron sulfide catalyst is first made more active by gas phase hydrogenation at high temperatures.
In U.S. Pat. No. 3,502,564, a metal sulfide catalyst, such as nickel, tin, molybdenum, cobalt, iron or vanadium, is taught as a catalyst for coal liquefaction. The sulfide catalyst is formed in-situ on the coal by the reaction of a metal salt with hydrogen sulfide.
Additionally, U.S. Pat. No. 4,013,545 teaches the hydrogenation and sulfiding of an oxidized metal of Group VIII in order to form a hydrocracker catalyst for oils.
Despite these efforts, the prior art has failed to provide an inexpensive, throw-away or once-through catalyst which has increased activity for the production of liquid products from the liquefaction or solvent refining of solid carbonaceous material, such as coal.